1. Field of the Invention
The present invention is related to magnetofluidic acceleration sensors, and more particularly, to an acceleration sensor with a wide frequency response and a high dynamic range.
2. Background Art
Magnetofluidic accelerometers are described in, e.g., U.S. patent application Ser. No. 10/836,624, filed May 3, 2004, U.S. patent application Ser. No. 10/836,186, filed May 3, 2004, U.S. patent application Ser. No. 10/422,170, filed May 21, 2003, U.S. patent application Ser. No. 10/209,197, filed Aug. 1, 2002 (now U.S. Pat. No. 6,731,268), U.S. patent application Ser. No. 09/511,831, filed Feb. 24, 2000 (now U.S. Pat. No. 6,466,200), and Russian patent application No. 99122838, filed Nov. 3, 1999. These accelerometers utilize magnetofluidic principles and an inertial body suspended in a magnetic fluid, to measure acceleration. Such an accelerometer often includes a sensor casing (sensor housing, or “vessel”), which is filled with magnetic fluid. An inertial body (“inertial object”) is suspended in the magnetic fluid. The accelerometer usually includes a number of drive coils (power coils) generating a magnetic field in the magnetic fluid, and a number of measuring coils to detect changes in the magnetic field due to relative motion of the inertial body.
When the power coils are energized and generate a magnetic field, the magnetic fluid attempts to position itself as close to the power coils as possible. This, in effect, results in suspending the inertial body in the approximate geometric center of the housing. When a force is applied to the accelerometer (or to whatever device the accelerometer is mounted on), so as to cause angular or linear acceleration, the inertial body attempts to remain in place. The inertial body therefore “presses” against the magnetic fluid, disturbing it and changing the distribution of the magnetic fields inside the magnetic fluid. This change in the magnetic field distribution is sensed by the measuring coils, and is then converted electronically to values of linear and angular acceleration. Knowing linear and angular acceleration, it is then possible, through straightforward mathematical operations, to calculate linear and angular velocity, and, if necessary, linear and angular position. Phrased another way, the accelerometer provides information about six degrees of freedom—three linear degrees of freedom (x, y, z), and three angular (or rotational) degrees of freedom (αx, αy, αz).
There are a number of applications where frequency response and dynamic range of the accelerometer are important. Dynamic range refers to the minimum and maximum acceleration (angular and/or linear) that the accelerometer can measure. Frequency response refers to the highest input vibration frequency that the accelerometer can measure (usually, in this context, frequency response to linear acceleration is more important than frequency response to angular acceleration, since linear vibration usually has a higher frequency than rotational vibration).
Accordingly, there is a need in the art for an accelerometer with a high dynamic range and a high frequency response.